The present invention relates to a control apparatus of an automated transmission mounted on a motor vehicle, and more particularly to the apparatus applied to the automated transmission having a plurality of transmission gear trains.
A manual type transmission (MT) for executing a gear change operation by a manual operation of a driver includes an input shaft connected to an engine and to which a plurality of drive gears are attached, and an output shaft connected to a drive wheel and to which a plurality of driven gears forming pairs together with the drive gears are attached, in which a plurality of transmission gear trains are provided between the input and output shafts. In the MT, a gear change operation, i.e., a shift change is performed through manually operating a switching mechanism such as a synchromesh mechanism for switching a gear train to another gear train in a plurality of transmission gear trains after disengaging a clutch at a time of changing gear, thereafter connecting the clutch to complete the gear change operation.
When automatically executing the shift change and the clutch operation by a hydraulic actuator, it is possible to obtain an automated manual transmission based on a structure of a manual type transmission. This type of automated manual transmission has an advantage that the number of the parts can be reduced in comparison with a normal torque converter type automatic transmission (AT) having a planetary gear in an automatic gear change mechanism so as to make it easy to lighten, and an advantages that a power transmitting efficiency of a drive system is higher than that of the automatic transmission of the normal torque converter type.
As this type of automated manual transmission (hereinafter, simply referred to as AMT) having a plurality of transmission gear trains, there is a structure having a main clutch provided between a crankshaft and an input shaft and switching thereof from an engaged condition to a disengaged condition, and vice versa, and a hydraulic bypass clutch of a multi-disc type for preventing a torque disconnection from the input shaft to the output shaft at the time of the gear change operation. For example, such an AMT is disclosed in Japanese Patent No. 2703169, in which an operation of the clutch in the manual type transmission is automated by a hydraulically driven actuator.
In the AMT, the structure is made such that one gear pair for transmitting a power is suitably switched by the synchromesh mechanism, and the engaged gear pair are switched while transmitting the torque from the input shaft to the output shaft by switching the bypass clutch to a connection state at the time of changing gear, thereby intending to prevent the torque disconnection at the time of the gear change operation.
However, in such an AMT, working fluid can not be supplied to actuators for performing a shift operation when there occurs a malfunction in a hydraulic pressure system including an oil pump as a hydraulic pressure generating source. As a result, there may occur a fear that a gear change operation can not be performed. Then, Japanese Patent Application Laid Open No. 2000-55184 discloses a return spring mounted on the actuator, which functions to shift a current gear range to a predetermined gear range for ensuring a safety travelling when an operating force due to hydraulic pressure is lost by a malfunction.
However, the conventional apparatus need to provided the return spring on the actuator, in which there is a problem that the structure of the apparatus becomes complicated. In addition, when the hydraulic pressure can not be supplied, the shift change is performed through forcibly moving a sleeve of a dog clutch or the synchromesh mechanism with the return spring. Accordingly, the conventional way has a drawback that the shift change can not be performed to gear ranges other than the gear range provided with the return spring, that is, function during a malfunction of the hydraulic pressure system is limited.
In other words, for example, if the return spring is set on the first speed gear range and there occurs a trouble of the hydraulic pressure system when travelling with high speed on an express-highway, an over-revolution of the engine causes a quick deceleration, or a burning of a starting clutch may occur due to a half-clutch. To the contrary, if the return spring is set on the fifth speed gear range and there occurs such a trouble when travelling with low speed, the engine speed may be extremely lowered to cause an engine stop, or the travelling of vehicle may stop due to a shortage of driving force since the starting clutch is in a state of half-clutch.
An object of the present invention is to enable a motor vehicle to keep a minimum travelling performance with a simple structure even when a malfunction of the hydraulic pressure system occurs.
In accordance with the present invention, there is provided a control apparatus of an automated manual transmission comprising an input shaft provided with a plurality of drive gears, an output shaft provided with a plurality of driven gears engaged with the drive gears, and actuators for switching a transmission gear train to transmit a power from the input shaft to the output shaft, the actuator being hydraulically driven comprising a hydraulic pressure generating source for generating hydraulic pressure of working fluid, a control valve for regulating the hydraulic pressure of working fluid for supplying to the actuators, pressure storing means for saving the working fluid supplied from the hydraulic pressure generating source and storing pressure energy, the pressure storing means being located between the control valve and the hydraulic pressure generating source, and transmission control means for switching the transmission gear train to a predetermined gear range with the pressure energy stored in the pressure storing means when a trouble of a hydraulic pressure system for supplying the working fluid occurs.
According to the present invention, even when any trouble occurs in the hydraulic pressure system, the working fluid can be supplied to the actuators since the hydraulic pressure is stored in an accumulator as pressure storing means, so that a minimum drive ability can be ensured even in such an emergency situation.
Further, the present invention is characterized in that the transmission control means determines that there occurs the trouble in the hydraulic pressure system due to a malfunction of the hydraulic pressure generating source when a rising rate of the hydraulic pressure in the working fluid is lower than a predetermined value in spite of an activating instruction sent to the hydraulic pressure generating source. Thereby, the malfunction of the hydraulic pressure generating source can be diagnosed without using a particular detecting device and with a cheap cost and accuracy.
In addition, the present invention is characterized in that the transmission control means switches the transmission gear train to the lowest speed gear range within a scope of no over-revolution of engine when the trouble in the hydraulic pressure system is detected. Thereby, in the both cases of high speed and low speed drives, there does not occur a disadvantage such as a quick deceleration, so that a safety traveling can be ensured.